Fillers and filler compositions are well known and widely used in papermaking applications in order to reduce paper costs by replacing more expensive virgin cellulosic fibers by less expensive filler. Fillers also make it possible to improve certain paper properties such as, for example, surface smoothness, printability and optical properties like opacity and brightness. However, other paper properties may be adversely affected. For instance, filled paper usually exhibit lower strength properties compared to unfilled paper. It would be advantageous to be able to provide a filler composition that imparts improved strength and other properties to paper. It would also be advantageous to be able to provide a method of preparing such a filler composition. It would also be advantageous to be able to provide filled paper exhibiting improved strength and other properties. It would also be advantageous to be able to provide an improved process of producing filled paper.